1. Basal Insulin
First of all, it’s totally normal that the amount of insulin in the body during the night might not be enough to prevent the blood sugar from rising, which means that something is wrong with the basal rate.
What do we need basal insulin for anyway?
Here is a quick recap of the basics: the liver continuously releases some sugar into the blood between meals, and at night, in order to keep the blood sugar at a healthy level.
Insulin is therefore needed for this sugar to be transported to the cells. The basal insulin that should normally make up 50-50% (with a variety of 40:60 to 60:40) [1] of our total insulin requirement is needed for this continuous flow of sugar.
And of course, the demand can also change over time. For example, if you catch a cold or have a fever - which everyone has probably noticed at some point when looking at their values.
Changes in the demand for insulin can also occur gradually. Gaining or losing weight, aging and hormone changes during the menopause for women, can all play a role.
2. Dawn Phenomenon
Normally, the basal insulin demand of almost everyone rises in the early hours of the morning (mostly between 3 a.m. and 6 a.m.) [2] This is normal.
However, the rise can vary in intensity. This is called the dawn phenomenon.
The reason for this is a more intense release of the growth hormones adrenalin, cortisol and glucagon, which are also known as the antagonists of insulin.
With basal insulin injections that cannot be adjusted on an hourly basis, this problem is often not easy to solve. However, an insulin pump can deliver more insulin when there is a higher demand.
3. Sleep Quality
Now onto the topic of sleep. Those who are stressed, those who sleep badly - and sometimes too little (less than 6 hours) - tend to have higher cortisol levels. [3]
It is important to remember that cortisol and insulin aren’t best friends, because cortisol counteracts the insulin which results in increased blood sugar values.
Approximately 1.5 hours after going to sleep, our insulin demand reduces. At night time, between 2 a.m. and 3 a.m., we have our lowest requirement for insulin.
When we get up, the demand rises sharply, which is again due to hormones that regulate our blood pressure. Those that wear a continuous glucose meter (CGM) can analyze these processes very well.
4. Dinner, Protein And Fat
Who doesn’t know the feeling of coming home late from work with monstrous hunger and having a huge meal right before going to sleep?
At night time, as we’re lying in bed, we are digesting very slowly and that late meal can end up taking revenge with a high fasting blood glucose value. Especially if the meal contains large amounts of protein and fat, such as steak with salad.
The protein content of our food has an influence on blood sugar values, but with a time delay. The rise in blood sugar is therefore very delayed.
Depending on the amount of protein, blood sugar rises after about 3-8 hours. Protein building blocks (amino acids) that have an effect on blood sugar are converted into glucose, but there are also amino acids that lead to an increased release of glucagon, which cause the liver to release more sugar.
So, the next time you have dinner, keep an eye on your protein-fat-calculations.
5. Forgotten Insulin
Watching a funny video on YouTube or binge-watching your favorite series on Netflix?
Most of the time, we combine time in front of the screen with yummy snacks to make for the perfect night in. And relaxation is good for you! This can be tricky however, because snacking in the late evening or at night can be a reason for high blood glucose values.
Especially if you forget the insulin. Tip: If possible don’t snack at all (ok, ok, maybe this isn’t so realistic ;)). But, if you do, then remember to inject your insulin.
Let’s look at an example. Each carbohydrate exchange, which is equal to 15 grams of carbs, causes a glucose rise between 35-60 mg/dl (1.9-3,4 mmol/l) in adults, and this can easily be reached with a few chips.
6. Too High Blood Sugar In The Evening
Some people start into the night with a high blood glucose value for various reasons. In this case, work towards getting your blood sugar close to your target range in the evening.
Your basal insulin dose is appropriate when your blood sugar stays steady or varies no more than 30 mg/dl. However, those who start into the night with a high blood glucose value often wake up with a high blood glucose value, as well.
7. Overnight Hypoglycemia
Last but not least, a high fasting blood sugar can also be caused by a hypo overnight. During a hypo, adrenaline is released which leads to a release of sugar from the liver and makes blood sugar rise with a time delay.
To prevent this, a nightly check of your blood glucose values between 2 a.m. and 3 a.m. can help.
[1] Rosak C et al, Angewandte Diabetologie 5. Auflage, 2014
Walsh J. Roberts R, Carma C, Bailey T, Using Insulin, 2003
Thomas A, Kolassa R, Sengbusch v. S, Danne T, CGM interpretieren, 2017, 1. Auflage
[2] https://de.wikipedia.org/wiki/Dawn-Ph%C3%A4nomen#:~:text=Unter%20dem%20Dawn%2DPh%C3%A4nomen%20(von,Gegenspielern%20des%20Insulins%20bedingt%20ist.
[3] Cappuccio, F. P., D’Elia, L., Strazzullo, P., & Miller, M. A. (2009). Quantity and Quality of Sleep and Incidence of Type 2 Diabetes: A systematic review and meta-analysis. Diabetes Care, 33(2), 414–420. doi:10.2337/dc09-1124 https://care.diabetesjournals.org/content/33/2/414
This article was updated in September 2020
